11                              Summary of Environmental outcomes and conclusions

The Emissions Control Project at CPB will result in significant emission reductions of SO2 and NOx.  Further reduction in particulate emissions is also anticipated as a result of SO2 emission control in addition to existing high efficiency ESP.

The construction and operation of the Project could also result in some environmental impacts which have been the subject of a detailed assessment under this Study.  They are summarised and discussed in the following sub-sections.

11.1                        Air Quality

11.1.1                  Construction Phase

Dust from excavation, site formation and construction activities is the only key air quality concern during the construction of the Project.  Owing to the small scale of the civil construction requirement and the distance from the ASRs, no adverse dust impact is anticipated.  In addition, only a limited number of diesel-powered equipment will be operated on site, and therefore impact from construction equipment is expected to be minimal.  With the implementation of the dust control measures stipulated in the Air Pollution Control (Construction Dust) Regulation, no adverse air quality impact is envisaged from the construction of the Project.

11.1.2                  Operational Phase

Except for a slight increase of emissions associated with marine traffic due to increased reagent and by-product transportation, the operation of the Project will not introduce any additional emissions of air pollutants, while the SO2 and NOx emissions will be significantly reduced.

The following reduction efficiencies are used as the basic assumptions for the operational air quality assessment:

·       SO2 emission reduction by up to 90%; and

·       NOx emission reduction by up to 80%.

A comparative air quality assessment was conducted for CPB by scale model testing performed in a Boundary Layer Wind Tunnel to simulate the behaviour of the exhaust plume before and after installation of the proposed emission control equipment.

The modelled percentage reduction in SO2 and NOx concentrations at the 36 ASR locations after implementation of the retrofit programme are similar in magnitude to the proposed emission reductions at source.  The effects of changes in flue gas characteristics on the dispersion of emissions were minor and insignificant when compared to the corresponding reductions in SO2 and NOx emissions from CPB after retrofit.

The comparative study demonstrated that all the identified ASRs will have an improvement in air quality after the retrofit as required in Section 3.4.1.2 of the Study Brief.

11.2                        Noise

11.2.1                  Construction Phase

The construction noise assessment conducted for the Project indicates that the predicted noise levels at the noise sensitive receivers (NSRs) are expected to range from 43 to 51 dB(A) and therefore within the noise criteria.  This is due mainly to the considerable separation distance and the screening offered by the topography and the existing buildings.  In view of the assessment results, the noise generated during the construction phase is not expected to cause any adverse impact and mitigation measures will not be required.

11.2.2                  Operational Phase

The noise levels at the identified NSRs (Sha Po Kong village and the planned holiday camp at Siu Lang Shui) from the operation of the Project have been predicted based on the specified maximum sound pressure levels (SPL) for the new equipment to be installed at CPB.  The results indicate that the identified NSRs will be subject to noise levels of up to 35 dB(A), which complies with both the stipulated daytime and night-time noise criteria.

The suppliers of the new equipment should guarantee the specified SPL by providing certificate of measurement and verify the SPL during testing and commissioning in accordance with international standard procedures.  If necessary, the suppliers should apply attenuation measures to achieve the guaranteed noise levels during the detailed design stage.  With the noise specifications in place, further mitigation measures will not be required during the operational phase of the Project.

11.3                        Water Quality

11.3.1                  Construction Phase

The water quality modelling works, with the assumption of no mitigation measures to be adopted, have indicated that for both the dry and wet seasons, no exceedances of the WQO and the evaluation criterion are predicted to occur during the dredging operations.  The impact assessment has also shown that other land-based construction works, if properly controlled, are not expected to cause any adverse impacts to the surrounding waters and the sensitive receivers. 

11.3.2                  Operational Phase

No effluent is anticipated from the operation of the NOx control system and water quality impact is not expected.

In the LS-FGD process, the gypsum slurry from the absorber unit is treated, resulting in dewatered gypsum and a small quantity of liquid effluent.  The resulting effluent may have a small chemical oxygen demand and/or reduced dissolved oxygen concentrations. 

The effluent will be treated to comply with the discharge standards stipulated in the Technical Memorandum on Standards for Effluents Discharged Into Drainage And Sewerage Systems, Inland And Coastal Waters issued under the Water Pollution Control Ordinance.  It will then be added to the cooling water flows and discharged via the existing sub-marine cooling water outfall of CPB, resulting in a small increase (about 0.02%) in the total flows from the outfall.  The treated FGD effluent would not be expected to have any adverse effect on the temperature of the cooling water or on the quantities of residual chlorine in the discharge.  The high degree of mixing inherent in the coastal margin or coastal zone will result in rapid dilution of the effluent to very low concentrations and no exceedance of the WQO or evaluation criteria for DO, dissolved metals, temperature, SS, salinity and sulphate are expected.  As a result, further mitigation measures are considered unnecessary.

11.4               Waste Management

11.4.1         Construction Phase

The key potential impacts during the construction phase are related to management of dredged sediments, demolition materials, excavated materials and construction waste.

About 80,700 m3 of uncontaminated sediment will be dredged to be disposed of at an open sea.  The final disposal site will be determined by the MFC and a dumping licence will be obtained from EPD prior to the commencement of the dredging works.

An estimated 50 m3 of potentially contaminated soil within the Project boundary will be treated and disposed of in accordance with the Remediation Action Plan (RAP). 

A total of about 835 tonnes of scrap steel will be produced during demolition of oil tanks and the associated fixtures/ appendages.  All the scrap steel will be delivered off-site by barge/truck for recycling. 

A total of about 30,000 m3 of excavated soil will be generated from the demolition and construction works.  All excavated soil will be reused for the backfilling on-site.

Small quantities of chemical wastes (less than 100 litres per month), sewage (a maximum of 135 m3 per day) and general refuse (a maximum of 585 kg per day) will be generated during the construction phase.

With the implementation of the mitigation measures recommended, the potential environmental impacts arising from storage, handling, collection, transport and disposal of wastes should be able to meet the criteria specified in the EIAO-TM.  No adverse waste management impact is anticipated.

11.4.2                  Operational Phase

About 240,000 tonnes of commercial grade gypsum will be generated each year from the FGD process and can be commercially recycled in PRD and East Asia region.  Similarly the lower grade gypsum (about 17,000 tonnes per year) can also be reused for cement production.  About 180 tonnes at 30% dry solids of sludge from FGD wastewater treatment is expected to be generated everyday.  Design optimisation of the FGD wastewater treatment system and exploration of additional disposal options, such as off-take by the limestone supplier and gypsum off-taker, are ongoing to further reduce the quantity of sludge to be disposed of at Government landfills.

With the implementation of the recommended mitigation measures, the potential environmental impacts associated with the storage, handling, collection, transport and disposal of a small quantity of industrial waste and general refuse arising from the operation of the Project will meet the criteria specified in the EIAO-TM and no adverse waste management impact is anticipated.

11.5                        Land Contamination

A number of existing facilities at CPB, including the FODT, the DG Store, the IPRS, the LPG compound and the CO2 tanks, are required to be demolished to accommodate the proposed emissions control equipment.  A land contamination assessment was carried out at these areas following the methodology and procedures prescribed in the Contamination Assessment Plan (CAP) approved by the EPD.   The land contamination assessment included soil and groundwater sampling, laboratory analyses for target parameters, preparation of Contamination Assessment Report (CAR) and preparation of Remediation Action Plan (RAP).

With the implementation of the remedial measures in the RAP, the hazard and environmental impacts associated with the potential land contamination and handling and treatment of the contaminated soil and groundwater are considered very low.

11.6                        Ecology

The land-based construction works and operations of the Project will be conducted entirely within the existing industrial site of CPPS and therefore no impact on terrestrial ecology is envisaged.

The literature review of the existing marine ecological resources of the Study Area identified two key sensitive receivers, namely the Sha Chau and Lung Kwu Chau Marine Park and the Indo-pacific humpback dolphin (Sousa chinensis) habitat.  The assessment of the potential construction and operational phase impacts to marine ecological resources has indicated that no significant adverse effects will impact the sensitive receivers as impacts arising from the proposed construction works are predicted to be confined to the area to be dredged and the area for the construction of the additional berthing facility, both of which have low ecological sensitivity.

The predicted alterations of the water quality parameters attributable to construction and operational activities are not expected to cause exceedances of the WQO, and therefore no impacts to the marine ecological resources or marine mammals are anticipated.

Mitigation measures designed to minimise impacts to the population of Indo-pacific humpback dolphins that use the area include restrictions on vessel speed while adopting local construction practice of using bubble curtains/jacket during percussive piling work for the construction of the additional berthing facility.  Other mitigation measures designed to mitigate impacts to water quality to acceptable levels (compliance with WQOs) are also expected to mitigate impacts to marine ecological resources.

11.7                        Landscape and Visual Considerations

With the new structures of the emissions control equipment located within the existing industrial setting of CPB, the Project is not expected to result in any negative impact on the surrounding landscape and it will also have a very low visibility.

11.8                        Conclusion

The Emissions Control Project at CPB will result in significant emission reductions of SO2 and NOx.  Further reduction in particulate emissions is also anticipated as a result of the LS FGD operation.

The detailed impact assessment concluded that no adverse environmental impacts are envisaged in the areas of air and water quality, noise, waste management, land contamination, ecology and visual appearance during both the construction and operational phases.